Research On Fermentation Of Fruit Beverages With Probiotics And Their Quality Change

Probiotic fermentation can improve nutritional and functional characteristics of raw fruits and vegetables,and open up the way of resource utilization.This research used grape and citrus as raw materials,researching on the process development of fruit probiotic fermented beverage,including the regulating effect of exogenous carbon sources on microbial growth and metabolism in grape ferment beverage and its bioactivity,the fermentation process of pure probiotics for grape ferment beverage,and step fermentation process of citrus beverage with probiotics.The specific results as follows:?1?Regulating effect of exogenous carbon sources?brown sugar,white sugar and honey?on microbial growth and metabolism in grape ferment beverage and its bioactivity was studied.The results showed that the addition of carbon source retarded yeast growth and ethanol metabolism,and simultaneously facilitated the growth of lactic acid bacteria and acid production.Among them,brown sugar and white sugar had strong inhibition ability on yeast growth and ethanol metabolism,the ethanol concentration reached 2.07%vol and 1.62%vol after fermentation respectively,which was significantly lower than honey group.Brown sugar could promote the growth of lactic acid bacteria and increase the total acid content and SOD activity.The p H value decreased from 4.16 to 3.83,and the SOD activity increased from71.68 U/m L to 91.05 U/m L after fermentation.In comparison with white sugar,honey and control group,adding brown sugar significantly increased the DPPH,ABTS⁺,·OH free radicals scavenging rate in grape ferment beverage.The raw grape juice contained a lot of tartaric acid and malic acid,but the addition of all carbon source significantly increased the content of malic acid and lactic acid,acetic acid and citric acid.Whereas,the content of tartaric acid decreased significantly by adding brown sugar,and it did not change much by adding white sugar and honey.In conclusion,the addition of brown sugar in grape ferment beverage was beneficial to improve the growth and metabolism of microorganisms and enhance the nutritional value of products.?2?The fermentation process of pure probiotics for grape ferment beverage was optimized.Lactobacillus plantarum was used as a strain to carry out the fermentation of grape ferment beverage with the additions of carbon source and nitrogen source.The results showed that the order of primary and secondary factors affecting sensory quality was initial sugar concentration,inoculum volume,nitrogen source concentration,fermentation time,the optimal value was 25%initial sugar concentration,0.3%nitrogen source concentration,inoculum volume 3%,fermentation time 60 h.The main organic acid of the grape ferment beverage was lactic acid after fermentation,which reached 15.74 g/L.The total phenolic contents and SOD activities were 2.34 mg/m L and 75.58 U/m L respectively.The fermented product has no ethanol production,and possesses strong DPPH radical scavenging activity,ABTS⁺radical scavenging activity,·OH radical scavenging activity and?-glucosidase inhibition potency,with bright red color,soft acidity and perfect taste.?3?Step fermentation process of citrus beverage with probiotics was studied for creating flavored and nutritious low-sugar fruit drink.The first step fermentation achieved desugaring by Monascus with the production of 5.3 AU₄₁₀extracellular pigments,which imparted bright orange color feature to the juice,simultaneously improving mouthfeel and nutrition.The total acidity decreased from 0.91 to 0.56 g/100m L for improving the taste in the second step fermentation with Candida utilis.Two step fermentation could increase the content of most polyphenols?gallic acid,chlorogenic acid,caffeic acid,ferulic acid?content and antioxidant capacity,and decreased the content of lactic acid,malic acid,citric acid,naringin and limonin in citrus juice.It suggested that the fermentation process could be a promising strategy for the deep processing of natural fruit juice.This study provides theoretical basis and guidance for the development of fruit fermented beverage processing,as well as related products.